Catheters are used for an ever-growing number of procedures. For example, catheters are used for diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, the catheter is manipulated through the patient's vasculature and to the intended site, for example, a site within the patient's heart. The catheter typically carries one or more electrodes, which may be used for ablation, diagnosis, or the like, as is well known to those skilled in the art.
In order to manipulate the catheter through a patient's vasculature, the catheter must be flexible. In addition, such catheters are preferably steerable, so that the clinician may temporarily impart a desired curve to the catheter from a remote location in order to pass through curved areas within a patient. A conventional steerable catheter includes one or more pull wires which extend through the catheter shaft, and connect to the catheter adjacent the distal end of the catheter at an off-axis location. The pull wires connect to a control knob or knobs, slide actuator, or other suitable manipulating member that is mounted in a control handle. A form of such a catheter is disclosed in U.S. Pat. No. 5,383,852 to Stevens-Wright and assigned to the assignee of the rights in the present invention, the disclosure of which is hereby expressly incorporated by reference.
While such catheters have gain widespread acceptance in the industry, they nevertheless suffer from certain shortcomings. One shortcoming is that to achieve relatively complex curves, those catheters require multiple pull wires which extend through different lumen and which connect to the catheter at different anchoring points. In addition, the pull wires each require a separate manipulating member to tension the respective pull wires. Thus, in a conventional steerable catheter, a relatively large amount of space is occupied by the steering subsystem, which limits the amount of space available for other components.
In addition, ablation catheters typically must assume various curves so that the ablation electrodes carried on the catheter will come into contact with a patient's tissue at selected locations. Thus, for that additional reason, catheters should be able to assume complex curves.
Others have designed catheters that achieve complex curves, for example, three-dimensional curves. One such catheter requires a secondary anchoring point, and a catheter shaft having a segment of intermediate stiffness and a more flexible segment, such that when the pull wires are tensioned, the catheter shaft assumes some relatively complex curve. However, to achieve such a curve, the catheter requires an intricate structure.
Accordingly, it will be apparent that there continues to be a need for a steerable catheter which can achieve relatively complex curves to facilitate manipulation of the catheter through a patient's vasculature and to an intended site. Moreover, the needs exists for such a catheter with a steering subsystem that occupies a relatively small amount of space within the catheter to accommodate a relatively large number of other components. The instant invention addresses these needs.